High Expression of FAM83B Predicts Poor Prognosis in Patients with Pancreatic Ductal Adenocarcinoma and Correlates with Cell Cycle and Cell Proliferation

Abstract

FAM83B (family with sequence similarity 83, member B) seems to emerge as a new class of players involved in the development of a variety of malignant tumors. Yet the molecular mechanisms are not well understood. The present study is intended to investigate the expression and function of FAM83B in pancreatic ductal adenocarcinoma (PDAC). In this study, we found that the expression of FAM83B was significantly increased both in PDAC cell lines and PDAC tumor tissues. FAM83B expression was positively related with advanced clinical stage and poor vital status. Higher FAM83B expression predicted shorter overall survival in PDAC patients, regardless of lymphatic metastasis status and histological differentiation. Actually, FAM83B may act as an independent prognostic indicator as well. What's more, down-regulation of FAM83B in PDAC cells contributed to G0/G1 phase arrest and inhibition of cell proliferation. Finally, a subcutaneous xenograft model indicated that knockdown of FAM83B significantly reduced the tumor volume in vivo. Our findings have provided supporting evidence for the potential molecular biomarker role of FAM83B in PDAC. It's of great interest and broad significance to target FAM83B in PDAC, which may conduce to develop a meaningful and effective strategy in the diagnosis and treatment of PDAC.

Keywords: FAM83B; GSEA; cell cycle arrest; cell proliferation; pancreatic ductal adenocarcinoma; prognosis; tumor growth..

Figure 1

The expression of FAM83B in PDAC cell lines and tissues. A. The expression of FAM83B was measured by real-time PCR in PDAC cell lines. ^** p<0.01. B-D. The relative expression of FAM83B was detected in PDAC tissues and adjacent non-tumor pancreas tissues in dataset GSE71729, GSE28735 and Renji Cohort 1 patients. Error bars in the scatter plots represent SD. E-F. FAM83B protein level was measured by immunohistochemistry in normal pancreas and PDAC tissue from The Human Protein Atlas website and Renji cohort 2. FAM83B: Family with sequence similarity 83, member B; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; PDAC: pancreatic ductal adenocarcinoma.

Figure 2

Kaplan-Meier analysis of overall survival in PDAC patients. A-D. Survival curves were generated using the Kaplan-Meier method and the log-rank test was used to evaluate the statistical significance of differences. Higher FAM83B expression predicted shorter overall survival of PDAC patients in GSE71729, TCGA-PAAD, Renji Cohort 1 and Renji Cohort 2. E-F. FAM83B expression was related with poor prognosis in PDAC patients, regardless of lymphatic metastasis status and histological differentiation

Figure 3

The forest plot of univariable and multivariable analyses of prognostic parameters for survival of PDAC patients in Renji cohort 2. A-B. The forest plot demonstrated the relation between overall survival and FAM83B expression as well as other clinical characteristics in PDAC patients using the univariable and multivariable analysis.

Figure 4

Down-regulation of FAM83B in PDAC cells leads to G1/S phase arrest and inhibition of cell proliferation and tumor growth. A. GSEA in GSE71729 tumor samples (median split according to FAM83B expression) indicated that 'CELL-CYCLE-PROCESS' pathway was enriched in patients with FAM83B-higher expression versus patients with FAM83B-lower expression. B. Knockdown efficiency was confirmed by real-time PCR in PANC-1 and AsPC-1 cell line. C. Down-regulation of FAM83B increased cell population at G₀/G₁ phase but decreased at S/G₂ phase by flow cytometry analysis in PANC-1 and AsPC-1 cells. D. Western blot indicated down-regulation of FAM83B reduced the protein expression of CDK4, CDK6, cyclin D1, and enhanced the expression of p21^Cip1. GAPDH was used as a loading control. E. The cell counting kit-8 assay indicated cell proliferation was blocked when FAM83B was reduced in PANC-1 and ASPC-1 cells.^*p<0.05; ^** p<0.01. The experiment was performed in six replicate wells for each group and all the experiments were conducted in triplicate. Error bars represented SEM. F-G. Down-regulation of FAM83B significantly reduced the PDAC tumor volume in the subcutaneous xenograft model (p=0.0194). Error bars represented SEM.